High Bonding Temperatures Greatly Improve Soy Adhesive Wet Strength

Abstract

Soy wood adhesive bond strengths reported in different literature studies are difficult to compare because a variety of temperatures and other conditions have been used for the bonding and testing step. Some reports have indicated bond strengths are sensitive to bonding temperature, but the reason(s) for this has not been intensively investigated. Although these prior studies differ in other ways (such as type of soy, wood species, and test method), the effect of bonding temperature has not been clearly examined, which is important for focusing commercial applications. A tensile shear test using two-parallel-ply veneer specimens with smooth maple was used to measure both the dry and wet cohesive strength of soy adhesives. Although the soy adhesives gave very good strengths and dry wood failure, they often have low wood failure and shear strengths under wet conditions when bonded at 120 • C. However, wet strength greatly increased as the bonding temperature increased (120, 150 and 180 • C) for these two-ply tests with. This study examined the use of different types of soys (flours, concentrates and isolates) and different bonding temperatures and bonding conditions to evacuate several possible mechanisms for this temperature sensitivity, with coalescence being the most likely.

Characterization and Performance of Soy-Based Adhesives Cured with Epoxy Resin

“…However, applications of soy-based adhesives are limited due to their poor water resistance [ 8 ]. Various efforts, including chemical and enzyme treatment, have been attempted to overcome this problem and to improve gluability under wet conditions [ 9 , 10 , 11 ]. Most of these efforts are one-pot reactions where the modifiers are added in the preparation process of soy-based adhesives.…”

Physico-Chemical Properties of Soybean Meal-Based Adhesives Reinforced by Ethylene Glycol Diglycidyl Ether and Modified Nanocrystalline Cellulose

“…The soybean meal (SM) mainly consists of protein, and with the advantages of renewability, biocompatibility, biodegradability, processability, and film-forming capacity, it has great potential to be used in wood industry, agriculture, bioscience, and biotechnology [ 4 , 5 , 6 ]. Soy-based adhesive is produced from the soybean meal, a processing residue of soybean when producing soybean oil and other soy-based food products, which were commercially used in the production of plywood from the 1930s to the 1960s [ 7 ].…”

Comparison of Canola and Soy Flour with Added Isocyanate as Wood Adhesives

“…Although improvement was observed in the canola bond strength with pMDI added before adding the water, we also wanted to look at the effect of bonding temperature with pMDI added to soy and canola flour after the water similar to our prior PAE studies (Frihart et al, 2016). Prior work has shown that soy adhesives are stronger when bonded at, or exposed to, higher temperatures without and with added PAE (Frihart et al, 2016). This was attributed to improved film coalescence, with the heat providing molecular mobility needed to entangle proteins and form additional bonds.…”